1. Field of the Invention
This invention relates to a finder for a video camera or the like, and particularly to a visual axis detecting finder for detecting a photographer's visual axis during operation of a camera.
2. Related Background Art
Cameras have been put on sale in which a focus position selected by a photographer is decided by detecting the photographer's visual axis have been put on sale.
A visual axis detecting apparatus is disclosed, for example, Japanese Laid-Open Patent Application No. 61-172,552. According to this publication, the center of pupil of a photographer's eye and the corneal reflected image (so-called Purkinje's image) of a light source for illuminating the eye are detected, and the direction to which the eye is directed is calculated from the relative relation between the Purkinje's image and the center of the pupil to thereby decide the direction of the visual axis.
Also, a finder in which visual axis detection and adjustment of the field of view of the finder are combined together is proposed, for example, in Japanese Laid-Open Patent Application No. 5-188,430.
This publication proposes a technique of moving some of the lenses constituting the eyepiece to effect diopter adjustment but so as not to affect visual axis detection in order to prevent any reduction in the accuracy of visual axis detection.
However, moving a part of the eyepiece in effecting diopter adjustment results in a variation of the size of the field of view and thus, an object in the field of view moves. Accordingly, when looking at a certain object, the visual axis deviates and it is necessary to detect the visual axis again. If a person's visual axis smoothly follows the object, it will be possible to detect the visual axis without so great a problem, but actually the visual axis may flicker or may sometimes move to different area. Particularly, in a finder of a high field magnification like an electronic viewfinder (EVF) in a video camera or the like, if a part of the eyepiece of the finder is moved, the variation in the field magnification will become great and the fluctuation of the visual axis will become great. Accordingly, in adjusting diopter, it is convenient to provide a finder which suffers little from a variation in the field magnification and in which the position of the object does not change.